Device for energy conversion

Abstract

The invention relates to a device for isothermal expansion and compression of a gas (3), ensuring the compression of said gas by consuming mechanical energy and the restitution of the mechanical energy by the expansion of said gas. The device comprises at least two liquid pistons (4, 41, 42) movable in at least two chambers (31, 32) each comprising a gas that is able to be compressed or expanded by movement of said liquid pistons. A mechanical actuator (1), comprising at least one solid piston, ensures the movement of the liquid pistons in the chambers. Each chamber comprises an insert (51, 52), through which said liquid (4) and said gas can circulate, the insert comprising through-cells (53), which extend in a direction parallel to the direction of movement of said liquid piston in said insert. The device comprises at least one first phase separator connected to an outlet of each of the chambers, and to a tank (5) for storing pressurized gas.

Description

[0001] The invention relates to a system for energy conversion and storage.

[0002] The compression and / or expansion of gas by liquid piston appears in the literature as a promising solution to increase the energy efficiency of energy production facilities, by seeking to achieve the most isothermal thermodynamic evolution possible.

[0003] We know of technologies, such as those described in patent application FR 3 036 887, which use pumps or turbines to achieve energy conversion between a mechanical actuator and the liquid of the liquid piston: one or more stages of liquid piston compression are implemented in such installations to cover the desired gas pressure range.

[0004] Various installations or devices can be deployed to increase heat exchange in the liquid piston compression chamber, such as water droplet spraying, implementation of multiple chambers in parallel, addition of a heat exchange insert, etc.

[0005] These installations generate certain problems: in particular, achieving a quasi-isothermal compression / expansion requires obtaining a significant heat exchange in the compression chambers during expansion and / or compression, the value of which is several orders of magnitude greater than the exchanges existing in conventional technologies.

[0006] The installations proposed in patent application FR 3 036 887 have lengthened the compression / expansion times, but they implement simple technical solutions to approach a near-isothermal operation. However, this results in large installations: they occupy a significant amount of space (on the order of 50,000 m³ for a power output of 15 MW), which can lead to substantial operating costs.

[0007] Other technologies offer more compact but more complex solutions to implement, which does not allow for a reduction in operating costs.

[0008] Thus, the level of complexity and the cost involved in such installations are obstacles to the development of such technologies. Documents US2010 / 329903A1 and US5771693 A disclose devices for the isothermal expansion and compression of a gas.

[0009] The invention offers an alternative solution that is simple to implement and can be scaled according to the applications for which it will be specifically designed.

[0010] The invention relates to an isothermal gas expansion and compression device, ensuring the compression of said gas by consuming mechanical energy and the release of mechanical energy by the expansion of said gas, said device comprising: at least one first and at least one second liquid pistons, movable in movement respectively in a first and a second chamber, each of said at least one first and second chambers comprising a gas, capable of being compressed or expanded under the effect of the movement of said at least one first or second liquid piston, an actuator, capable of ensuring the movement of said at least one first and second liquid pistons in said first and second chambers, each of said at least one first and second chambers comprising respectively at least one first and at least one second perforated insert, through which said liquid and said gas can circulate.

[0011] The device according to the invention is remarkable in that the actuator is a mechanical actuator comprising at least one solid piston, and in that the perforated insert comprises through cells extending between a first cell opening at one end of the insert and a second cell opening at the other end of the insert, the cells being oriented in a direction that is either parallel to the direction of movement of the liquid piston in the insert or inclined relative to the direction of movement of the liquid piston. Finally, the device further comprises at least one first phase separator connected to a first outlet of the first chamber and to a second outlet of the second chamber.

[0012] Advantageously, the phase separator is connected to a pressurized gas storage tank.

[0013] According to an advantageous embodiment, the device according to the invention comprises a second separator, connected to said first and second outlets of said first and second chambers respectively, in that said first separator comprises a first internal pressure which corresponds to the internal pressure of the gas contained in said pressurized gas reservoir and in that said second separator comprises a second internal pressure which corresponds to atmospheric pressure.

[0014] Preferably, the first and second separators are in fluidic communication with each other to allow the passage of liquid from the first separator to the second separator.

[0015] Preferably, the device includes a first air intake device ensuring the passage of air at atmospheric pressure between said at least one first chamber and said second separator, as well as a second air intake device at atmospheric pressure between said at least one second chamber and said second separator.

[0016] In addition, the device includes a third air intake device ensuring the passage of compressed air between said first chamber and said first separator, as well as a fourth compressed air intake device between said second chamber and said first separator.

[0017] Preferably, the device includes a first low-flow regulating valve ensuring the passage of fluids from said first separator to said first chamber, and a second low-flow regulating valve ensuring the passage of fluids from said first separator to said second chamber.

[0018] According to an advantageous embodiment, the device includes a regulating valve set at a safety pressure between said first chamber and said first separator and / or between said second chamber and said first separator, to allow the evacuation of a volume of liquid from said at least one first or second liquid piston to the first separator.

[0019] In addition, each of the first and second chambers is preferably also fluidly connected to a fluid / fluid exchanger which allows said at least one first and second liquid pistons, respectively, to be kept at ambient temperature, preferably with a tolerated temperature variation of plus or minus 10 °C, said fluid / fluid exchanger preferably comprising a pump, a fluid / air exchanger or a fluid / fluid exchanger, possibly a motor-fan if said exchanger is a fluid / air exchanger and possibly at least one regulating valve.

[0020] Advantageously, the insert has a core of structural material comprising an expanded honeycomb structure.

[0021] Even more advantageously, the said mechanical actuator includes a magnetically actuated linear motor.

[0022] According to one embodiment, said mechanical actuator comprises a motor associated with a crankshaft.

[0023] According to yet another embodiment variant, the said mechanical actuator comprises a motor associated with a worm gear.

[0024] The invention also relates to an installation comprising at least two devices as defined above, said mechanical actuators of said at least two devices being mechanically linked to operate together, and in this the installation comprising a first phase separator common to said at least two devices, said first common phase separator being connected to a first outlet of the first chambers of the devices and to a second outlet of the second chambers of said devices, said first phase separator being connected to a common pressurized gas storage tank.

[0025] In an embodiment where the installation comprises at least two devices including two phase separators, the second separator being common to said at least two devices, said second separator is connected to said first and second outlets of said first and second chambers of each of said at least two devices, said first common separator includes a first internal pressure which corresponds to the internal pressure of the gas included in said common pressurized gas reservoir and said second separator includes a second internal pressure which corresponds to atmospheric pressure.

[0026] The invention also relates to a method for implementing a device as defined above, the method comprising the following steps: actuation of the mechanical actuator, displacement of said at least one solid piston causing said first liquid piston to move in said first chamber and said second liquid piston in said second chamber, said first and second liquid pistons being driven in opposite directions, the first liquid piston compressing said gas in the insert of said first chamber up to a first predetermined pressure, the second liquid piston creating a vacuum in said insert of said second chamber up to a second pressure, when said first pressure is reached, opening of an air intake device between said first chamber and said first phase separator to evacuate the pressurized gas from the first chamber to said first separator until said liquid piston completely passes through said insert and reaches the first outlet of the first chamber and simultaneously the air intake into said second chamber.

[0027] The device according to the invention is thus a type of reversible gas compressor, which allows a gas to be compressed by consuming mechanical energy, but also to be released by expanding a gas. The thermodynamic evolution of the gas is nearly isothermal, allowing these pressure variations to be performed with low energy loss thanks to compression / expansion by liquid piston. The nature of the gas and the liquid can be adapted to the needs of the application for which the device is intended (air, hydrogen, methane, gas, water, etc.).

[0028] In compression mode, within the framework of a non-limiting embodiment that will be presented later, the principle is based on the compression of the gas by a liquid piston, the latter being driven by a solid piston. The solid piston is actuated directly by a linear motor, of which it constitutes the moving driving part containing the magnets, or by another piston movement system (connecting rod, crank, rack and pinion, etc.). Thus, by moving, the solid piston pushes a liquid piston in a closed compression chamber (vertical cylinder). The reduction in volume causes the gas to be compressed.

[0029] The cylindrical compression chambers are subdivided into many small volumes by means of a heat exchange insert consisting of an extruded 2D pattern, whose cells extend in the direction of the liquid piston (structure also called "honeycomb", in aluminum or other heat-conducting material).

[0030] Thus, the fluid characteristics of the liquid piston allow a small liquid piston to form in each cell of this honeycomb structure, while ensuring a perfect seal between the liquid and gaseous environments. The presence of the insert (honeycomb) provides a very large contact surface with the gas and allows for significant heat exchange. The heat exchange between the gas and the insert, the heat transfer within the insert, and its own heat capacity allow the gas temperature to be maintained during compression at a value close to the initial temperature of the entire system (quasi-isothermal).

[0031] The heat exchange insert thus acts as a regenerative exchanger, successively allowing the transfer of thermal energy from the gas to the insert by convection / conduction, the storage of thermal energy thanks to a moderate increase in its temperature (effect of its thermal capacity) and then the transfer of this thermal energy to the liquid by convection / conduction.

[0032] Other advantages and features of the invention will become apparent upon examination of the detailed description of a non-limiting embodiment and the accompanying drawings, in which: [ Fig. 1 ] is a schematic representation of a first embodiment of a device according to the invention, seen from the side, [ Fig. 2 ] is a schematic representation of a second embodiment of a device according to the invention, seen from the side, [ Fig. 3 ] is yet another schematic representation of a third embodiment of a device according to the invention, seen from the side, [ Fig. 4 ] shows an example of an installation according to the invention, implementing several devices according to the invention, seen in perspective, [ Fig. 5 ] is yet another schematic representation of a fourth embodiment of a device according to the invention, viewed from above, and [ Fig. 6 [ ] is an example of an insert with a honeycomb structure, deployed, positioned in a chamber of a device according to the invention, the insert in the chamber being viewed from below. figure 1 illustrates an embodiment of a device according to the invention, allowing a gas to be expanded and compressed, enabling mechanical energy to be stored and released.

[0033] The device thus includes a mechanical actuator 1, which includes for example a crankshaft 10 (mechanical component ensuring the conversion of a linear reciprocating motion into a continuous rotation according to the connecting rod 11 / crank 12 system, and ensuring the conversion of a continuous rotational motion into a linear reciprocating motion).

[0034] A motor, not shown, converts the energy source. Generally, the energy source is electricity. However, another source could be used to generate rotational force.

[0035] It should be noted that the system does not require a "starter" to initiate rotation: for example in energy release mode (expansion), the crankshaft is set into rotation directly by the compression / expansion chambers, without assistance from the electric motor / generator.

[0036] The crank 12 is connected to two solid pistons 21 and 22, each being mounted to move mobilarily in a first chamber 31 and in a second chamber 32 respectively.

[0037] Each chamber 31 and 32 has a liquid piston 41 and 42, respectively, which is moved in the chamber by being pushed by the solid piston 21 and 22 which moves in the same chamber.

[0038] Each of the first and second chambers 31 and 32 are made of bent tubes, featuring: a first part of tube 33 and 34, respectively, which extends in a substantially horizontal direction, and a second part of tube 35 and 36, respectively, which extends in a substantially vertical direction.

[0039] It should be understood that the invention is not limited to the implementation of angled chambers (in other words, they could have a different shape without going out of the scope of the invention).

[0040] The two solid pistons 21 and 22 are mobile in displacement in the first part of tube 33 and 34, respectively, by being driven in displacement by the actuator 1.

[0041] The two liquid pistons 41 and 42 are mobile in movement in the first (33, 34) and second (35, 36) tube parts of the chambers 31 and 32, when they are pushed or sucked in by the movement of the solid piston 21 or 22 associated with them.

[0042] The second parts of tubes 35 and 36 are designed to receive and discharge a gas 3, for example air, so that the movement of the liquid 4 of the liquid pistons 41 or 42 in the chambers 31 and 32 causes either the compression of the gas 3 or an expansion of the gas 3.

[0043] To achieve this, each of the chambers 31 and 32 includes an outlet opening 37 and 38, respectively, ensuring in particular the entry and exit of gas into the second parts of tubes 35 and 36 of the first and second chambers 31 and 32.

[0044] The first and second outlets 37 and 38 are connected to a phase separator 2, which allows the gas 3 to be received and possibly a little liquid 4 from the liquid evacuated from chambers 1 and 2.

[0045] Phase separator 2 is connected to a pressurized gas storage tank 5.

[0046] The circulation of gas 3 and possibly liquid 4 between the phase separator 2, chambers 31 and 32 and the storage tank will be explained later.

[0047] The second parts of tubes 35 and 36 each accommodate an insert 51 and 52.

[0048] Inserts 51 and 52 are openwork inserts, that is to say, they each have cells in which the liquid from the liquid pistons 41 and 42 can circulate and which can also accommodate the compressed or expanded gas in the chambers 31 and 32.

[0049] Inserts 51 and 52 are unique: they are made from a deployable sandwich material core, resulting in an insert where the cells extend throughout its entire length. The core of the deployable sandwich material is composed of numerous layers of plastically deformable materials, joined together by bonding points (welds, adhesives, etc.) that extend along lines running the full length of the layers. By separating the two outer layers of the sandwich structure, cells are created between two adjacent material layers and the bonding lines, resulting in cells that extend along the entire length of the multilayer structure.

[0050] According to an alternative embodiment (not illustrated), the inserts could be made with a winding of stacked metal sheets, the stacked metal sheets comprising for example a flat sheet and a corrugated sheet (forming a succession of hollows and bumps) positioned one on top of the other and rolled together: the cells are then formed between the hollows of the corrugated sheet and the surface of the adjacent sheet, the cells then extending in the direction of movement of the liquid piston in the chamber which receives the insert.

[0051] Thus, the insert used in the context of the invention has so-called "through-cells," meaning that each cell has two openings, one at each end of the cell, with a first cell opening that leads to one end of the insert and a second opening that leads to the other end of the insert: the figure 6 shows the second part of tube 35 (or 36) of a chamber 31 (or 32) which has been cut to better show the insert 51 or 52.

[0052] Each of the inserts 51 or 52 is preferably made of aluminum and comprises contiguous cells 53 which together form a honeycomb pattern, and which include a first end opening 54 (visible in the figure), through which the gas 3 or the liquid 4 can enter or exit the insert. Another opening (not visible in the figure, but schematically illustrated by an arrow 55) opens near the outlet opening 37 and 38 of each of the chambers 31 and 32.

[0053] Each cell 53 of the structure of the insert 51 or 52 forms a mini-tube into which gas 3 and liquid 4 can enter and exit, each mini-tube being oriented parallel or mainly parallel to the direction of movement of the liquid 4 and the gas 3 in the chamber 31 or 32 (more precisely each mini-tube has an axis parallel to that of the second part of the tube 35 or 36 which receives it).

[0054] The term "primarily parallel" refers to a geometric orientation between the entry and exit points of a cell relative to the insert's axis. This orientation is either parallel or nearly parallel to the insert's axis, or inclined relative to it, due to the shape of the cell's mini-tube. Indeed, the cell can be straight, in which case the mini-tube is cylindrical, but the cell can also be twisted, with the mini-tube forming a helix.

[0055] On the figure 1 Also illustrated are two fluid / fluid exchangers 71 and 72: each of the first and second chambers 31 and 32 contains a fluid / fluid exchanger 71 and 72, respectively (represented in the bend of chambers 31 and 32 in the figure). The fluids are preferably water.

[0056] In this example, these fluid / fluid exchangers 71 and 72 are each connected to a pump 83, a fluid / air exchanger 84, a motor fan 85 and control valves 86. The assembly ensures that the liquid 4 (liquid pistons) is maintained at a temperature close to ambient temperature plus or minus 10 degrees Celsius.

[0057] A single pump could be used without departing from the scope of the invention. Similarly, the fluid / air heat exchanger 84 could be replaced by a fluid / fluid heat exchanger.

[0058] Pump 83, fluid / air heat exchanger 84, motor fan 85 and control valves 86 were not shown on the figure 1 However, they are found in the implementation method illustrated in figure 3 These elements ensure that the fluid in the cooling loop is maintained at a temperature close to ambient temperature, plus or minus 5 degrees Celsius.

[0059] The operating mode of the device shown in figure 1 The following is now presented: The motor of the mechanical actuator is, for example, a permanent magnet synchronous rotary motor, and is possibly associated with a reversible speed reducer (target speed of 30 rpm).

[0060] Such an engine allows the crankshaft 10 to rotate: the connecting rods 11 which connect the crankshaft to each solid piston 21 and 22 drive the solid pistons 21 and 22 in linear movement alternately: when the piston 21 is pulled, the piston 22 is pushed, and vice versa.

[0061] The operating principle in compression mode is as follows: the solid piston 21 pushes the liquid piston 41 into the closed chamber 31. The decrease in the volume of gas, pushed by the liquid piston 41 into the insert 51, increases the gas pressure in the insert 51.

[0062] Each cell 53 acts as a small liquid piston while ensuring a perfect seal between the liquid and gaseous environments. The insert 51 functions as a regenerative heat exchanger between the gas and the fluid of the liquid pistons. The presence of the insert 51 thus provides a large contact surface with the gas 3 and allows for significant heat exchange potential: the heat exchange between the gas and the insert, the heat transfer within the insert, and its own heat capacity allow the gas temperature during compression to be maintained at a value close to the initial temperature of the system: this is why the operation is considered quasi-isothermal.

[0063] When the air pressure reaches the desired value, a non-return valve 13 opens allowing the compressed gas 3 to escape out of chamber 31.

[0064] The liquid piston 41 continues its upward movement in chamber 31 until it touches an end wall of the chamber, thus releasing all the compressed gas 3. The solid piston, having reached the end of its stroke, changes direction, and the same process is repeated on the second piston 22 of the device, which is made of exactly the same components. The downward movement of the liquid piston 41 after the end of compression in the first chamber 31 allows low-pressure gas 3 to be admitted into this chamber 31 through the opening of another valve 14 (non-return valve).

[0065] Regarding the thermal energy captured in the gas by the insert 51 (the honeycomb structure) during compression, this energy caused the temperature of the insert 51 to rise by a few degrees Celsius, reflecting the storage of this thermal energy in the material.

[0066] The rise of the liquid piston 41, filling the entire volume of the chamber 31 at the end of compression, thus allows the thermal insert 51, charged with thermal energy, to come into contact with the liquid 4.

[0067] Since the solid / liquid heat transfer between the insert 51 and the liquid 4 of the liquid piston 41 is much more powerful than that between the solid / gas between the insert 51 and the gas 3, a significant heat exchange occurs between the walls and the liquid 4, causing the insert 51 - liquid 3 assembly to tend towards a slightly higher equilibrium temperature (on the order of a tenth of a degree above the initial temperature of the liquid) and therefore lower than the temperature of the insert 51 before contact with the liquid 4.

[0068] When a new volume of gas 3 is admitted to be compressed, the liquid 4 forming the descending liquid piston 41 passes through the fluid / fluid heat exchanger 71, which has the role of maintaining the temperature of the liquid piston 41 stable over time.

[0069] At the exit of chamber 31, the compressed gas 3 passes through the gas / liquid separator 2, possibly allowing the collection of a fraction of the liquid 4 constituting the liquid piston in the event of exceeding the top dead center of chamber 31.

[0070] At the outlet of this separator 2, the gas 3 is conveyed to its storage or to another gas compression stage in the storage tank 5.

[0071] The liquid 4 retained in the separator helps to constitute a reserve of liquid for the pistons 41 and 42, a fraction of which can be redirected to the compression chambers 31 and 32 in order to maintain a volume of liquid capable of ensuring the continuous operation of the system.

[0072] Valves 13 and 16 are connected between the gas / liquid separator 2 (whose internal pressure is equal to the gas compression pressure) and the base of the compression chamber 31 (whose pressure varies between the intake pressure and the maximum pressure). Valves 13 and 16 allow the transfer of compressed gas between the compression chambers and the separator; this gas may contain a fraction of fluid from the liquid piston.

[0073] It should be noted that the outlet 38 of chamber 32 also includes two check valves 15 and 16: valve 15 ensures an air supply at atmospheric pressure (or at low pressure).

[0074] Valves 13, 14, 15 and 16 can be replaced by pilot-operated valves.

[0075] Reference will now be made to the operating principle in gas expansion mode 3.

[0076] The reverse operation of the device, that is, as a converter of pressure energy to electrical energy, operates on the same general principle and is possible thanks to the embodiment illustrated in figure 2 By replacing the check valves 13 to 16 with pilot-operated valves 64, 61, 62 and 65: The compression chamber 32, initially full of liquid, admits a volume of pressurized gas 3 through valve 65

[0077] The pressure applied to the liquid piston 42 is applied to the solid piston 22, generating mechanical work.

[0078] This mechanical work is converted into electricity by the crankshaft / generator assembly.

[0079] When the volume of pressurized gas 3 admitted is sufficient, the valve 65 closes and the expansion of the gas 3 continues to move the solid piston 22.

[0080] The movement (and energy conversion) stops when the gas 3 reaches a pressure close to the bottom pressure (usually atmospheric). During the intake and expansion phases, the opposing liquid piston 41 moves from its bottom position to its top position, expelling the expanded gas 3 at atmospheric pressure outwards through the valve 61.

[0081] Chamber 32 is thus a relaxation chamber, and the heat exchange insert 52 is here cooled by gas 3 during the expansion while maintaining the expansion of gas 3 following a quasi-isothermal evolution.

[0082] The liquid / liquid exchanger 12 then allows the heating of the liquid piston 42.

[0083] The method of implementation shown in figure 2 includes a second atmospheric pressure phase separator 6 which allows, during the descent of the liquid piston 42 (or 41, when the liquid piston 42 acts by compressing the gas 3) to collect any fraction of liquid 4 coming from the liquid piston 41 or 42, but at low pressure.

[0084] In the embodiment illustrated in figure 2 , the mechanical actuator comprises a single solid piston 23 which moves either in one direction in chamber 31 or in the opposite direction in chamber 32.

[0085] This is a magnetic piston for a linear motor.

[0086] The operating mode is the same as that described for the device shown in figure 1 .

[0087] The difference lies in the presence of this second low-pressure phase separator 6.

[0088] As previously seen, the phase separators 2 and 6 have the role of recovering the liquid 4 expelled at the end of the stroke of the liquid piston 41 or 42 while allowing the gas 3 to continue its path.

[0089] The volume of separators 2 and 6 is chosen so that the velocity of gas 3 decreases sufficiently so that liquid 4 falls naturally to the bottom of the buffer volume.

[0090] Other complementary solutions can be considered, including the use of cyclonic systems or coalescing grids. The pressure drop of the gas in this element must remain low.

[0091] A hydraulic connection 20 between the phase separator 2 and the bottom of the compression chambers 31 and 32 (this can be in the second part of the vertical tube 35 and 36, or in the first part of the horizontal tube 33 and 34), allows a small flow of liquid 4 to be continuously admitted, compensating for losses by entrainment during the flushing.

[0092] A flow control valve 24 fitted to each hydraulic connection allows this flow rate to be varied in order to experimentally find the optimal setting.

[0093] Each liquid piston 41 and 42 has a valve 61 and 62 (respectively) allowing the liquid 4 to escape to the second unpressurized separator 6 in case of overpressure in chamber 31 and / or 32.

[0094] A lift pump 63 between the two separators 2 and 6 allows the lost liquid 4 in expansion mode in the unpressurized separator 6 during the exhaust of the gas 3 at atmospheric pressure to be returned to the pressurized separator 2.

[0095] Two other valves 64 and 65 allow the compressed gas to be transferred between the compression chambers 31 and 32 and the separator 2, the gas being able to include a fraction of fluid from the liquid piston.

[0096] If the liquid buffer volume 4 is sufficient, the operation of pump 63 is intermittent and infrequent. The regulation of this pump is based on the liquid levels in the two separators 2 and 6.

[0097] The method of implementation illustrated in figure 3 concerns the implementation of a device comprising three solid pistons with six liquid pistons: the principle of the "double acting" piston allows here to optimize the use of the mechanical parts.

[0098] Indeed, it is possible to achieve significant power outputs (several tens or hundreds of MW) by increasing the number of pistons. It may also be possible to increase power output by drastically increasing the diameter of the pistons and chambers, but increasing the number of pistons and chambers is generally preferred. Firstly, there is an optimal, economically viable size for a device that is easily transportable (for example, a piston diameter between 300 mm and 2,000 mm for high-power versions). Secondly, increasing the number of pistons reduces the amplitude of power fluctuations exchanged with the grid if a judiciously established phase shift exists between pairs of pistons. The system's outlet pressure can also be increased by staggering the compression stages using a cascade of compressors, as described below.

[0099] In the case of stages where the intake pressure exceeds atmospheric pressure (for high-pressure compression), the piston translation system design can advantageously utilize 1-to-1 coupling, with opposing pistons. This is because the high-pressure intake force in one chamber is counterbalanced by the higher-pressure compression force in the opposite chamber.

[0100] More specifically, the double-acting operation has advantages: the high-pressure intake force of one chamber is directly reused in the higher-pressure compression force in the opposite chamber without passing through mechanical power elements such as the connecting rod, crankshaft or engine / generator.

[0101] Generally speaking, whether single-acting or double-acting, increasing the number of solid pistons attached to the same crankshaft, but cleverly staggered, helps to limit torque and power variations during system operation. Limiting these variations reduces stress on the components, increasing overall reliability and reducing the need for oversizing.

[0102] The mechanical actuator 1 of the device shown in figure 3 It thus comprises three pistons, of which only one (piston 25) is represented (the pistons are out of phase by 120°) on the mechanical actuator.

[0103] This embodiment allows for a higher pressure to be achieved than that achieved by the embodiments shown in figures 1 et 2 In this embodiment, three successive compression or expansion stages are implemented, each compression chamber corresponding to a specific compression stage to be reached. For example, the first chamber has a compression stage of 11 bar, the second chamber has a stage that can increase the compression from 11 bar to 70 bar, and the third chamber allows the compression to increase from 70 bar to 300 bar.

[0104] It is also possible to allow two of these chambers to constitute medium pressure and high pressure stages.

[0105] The method of implementation illustrated in figure 3 includes in particular a first regulating valve 91 set at a safety pressure between said first chamber 31 and said first separator 2 and a second regulating valve 92 set at a safety pressure between said second chamber 32 and said first separator 2, to allow the evacuation of a volume of liquid from said at least one first or second liquid piston to the first separator 2.

[0106] There figure 4 illustrates an installation according to the invention, which includes a series of devices according to the invention.

[0107] A common crankshaft type mechanical actuator allows twelve pairs of solid pistons 21 and 22, mobile in twelve pairs of chambers 31, 32, to be actuated by the movements of the cranks 12 mounted on a mobile shaft rotating around its axis, the cranks being connected to the solid pistons 21 and 22 by means of the connecting rods 11.

[0108] It is noted that all the outlet openings 37 and 38 of chambers 31 and 38 are connected together to a first phase separator 2 and to a second phase separator 6 at atmospheric pressure: in other words, the pressurized phase separator 2 is connected: to the valves 64 of chambers 31, the valves 64 being all connected to the same drain pipe and to the valves 65 of chambers 32, the valves 65 being all connected to another common drain pipe.

[0109] Furthermore, all the valves 61 in chambers 31 are connected to another common drain pipe, which is connected to the second separator, and all the valves 62 in chambers 32 are also connected to another common drain pipe, itself connected to the second atmospheric pressure separator 6. It should be noted that valves 61 and 62 are low-pressure (or atmospheric pressure) air intake valves on the figures 2 , 3 et 4 They perform the same function as valves 14 and 15 shown on the figure 1 .

[0110] In this example of an embodiment, it is planned that the solid pistons 21 and 22 will have a diameter of 2.5 m and a stroke of 1 m.

[0111] The discharge pressure is approximately 11 bar, the inlet pressure 1 bar, and the compression time 1 second. A motor is used to operate the mechanical actuator. However, in addition, two smaller motor / pump assemblies, with lower power output compared to the main motor, are required to operate the cooling circuit (pump 83) and to transfer liquid 4 from separator 6 to separator 3 (pump 63). The shaft rotation speed is approximately 30 rpm.

[0112] The overall footprint of such an installation is approximately 7m high, 8m wide and 45m long.

[0113] An average power of 15MW is achieved with a variation amplitude of less than 0.8MW at a frequency of 12Hz.

[0114] The time to reach full power is on the order of one second (going from 10% to 100% of nominal power).

[0115] A start-up time (from total stop to 100% of nominal power) of approximately ten seconds is expected.

[0116] Once started, the system's power output can be easily adjusted by changing the engine / generator's (and therefore the crankshaft's) rotational speed or by adjusting the control of valves 61, 62, 64, and 65. This allows for a power range of 20% to 100% of the rated power, with a rapid response time (on the order of a second). figure 5This illustrates yet another embodiment with five chambers 31, 31', 31", 32, 32' arranged in a star configuration, coupled with double-acting pistons 26: The use of double-acting cylinders / pistons 26 allows for both increased power for the same number of pistons and better management of fluid leakage through the piston rings. Indeed, the fluid passing through the piston seals simply flows into the opposite chamber without the need to drain the leaked fluid.

[0117] It is understood from the preceding description how the invention makes it possible to transform a mechanical movement into the pressurization energy of a gas and how this energy can be used to generate a mechanical movement.

[0118] It should be understood that the invention is not limited to the implementation of the examples specifically described and illustrated above and that it extends to the implementation of any equivalent means.

[0119] In particular, the application of the process is not specific to air and water. Other applications are envisaged by the invention, such as the compression / expansion of (H2, CO2, CH4...) with water as the liquid piston fluid, but also ionic liquids, solvents, oils, organic liquids...

Claims

1. A device for the isothermal expansion and compression of a gas (3), ensuring the compression of said gas (3) by consuming mechanical energy and the restitution of mechanical energy by the expansion of said gas (3), said device comprising: - at least one first and at least one second liquid pistons (4, 41, 42), movable respectively in a first and a second chamber (31, 32), each of said at least one first and second chambers (31, 32) comprising a gas (3), able to be compressed or expanded under the effect of the movement of said at least one first or second liquid piston (4, 41, 42), - an actuator (1) capable of moving said at least one first and second liquid pistons (4, 41, 42) in said first and second chambers (31, 32), each of said at least one first and second chambers (31, 32) comprising respectively at least one first and at least one second apertured insert (51, 52) through which said liquid (4) and said gas (3) can flow, characterized in that said actuator (1) is a mechanical actuator comprising at least one solid piston (21, 22), in that said apertured insert (51, 52) comprises through-cells (53), which extend between a first cell opening (54) opening out at one end of said insert (51, 52) and a second cell opening (55) opening out at a second end of said insert (51, 52), said cells (53) being oriented in a direction which is either parallel to the direction of movement of said liquid piston (41, 42) in said insert (51, 52) or inclined with respect to the direction of movement of said liquid piston, and in that said device further comprises at least a first phase separator (2) connected to a first outlet (37) of said first chamber (31) and to a second outlet (38) of said second chamber (32).

2. The device according to claim 1, where said phase separator (2) is connected to a pressurized gas (3) storage tank (5).

3. The device according to claim 2, comprising a second separator (6), connected to said first and second outlets (37, 38) of said first and second chambers (31, 32), respectively, where said first separator (2) comprises a first internal pressure which corresponds to the internal pressure of the gas (3) comprised in said pressurized gas reservoir (5) and said second separator (6) comprises a second internal pressure which corresponds to atmospheric pressure.

4. The device according to claim 3, where said first and second separators (2, 6) are in fluid communication with one another to allow liquid (4) to pass from the first separator (2) to the second separator (6).

5. The device according to either one of claims 3 or 4, comprising a first air intake device (61) ensuring the passage of air at atmospheric pressure between said at least one first chamber (31) and said second separator (6) and a second air intake device (62) at atmospheric pressure between said at least one second chamber (32) and said second separator.

6. The device according to any one of claims 3, 4 or 5, comprising a third air intake device (13, 64) ensuring the passage of compressed air between said first chamber (31) and said first separator (2) and a fourth compressed air intake device (16, 65) between said second chamber and said first separator (2).

7. The device according to any one of claims 3 to 6, comprising a first low-flow control valve (24) ensuring the passage of fluids from said first separator (2) to said first chamber (31) and a second low-flow control valve (24) ensuring the passage of fluids from said first separator (2) to said second chamber (32).

8. The device according to any one of claims 3 to 7, comprising a regulating valve (91, 92) set at a safety pressure between said first chamber (31) and said first separator (2) and / or between said second chamber (32) and said first separator (2), to enable a volume of liquid to be discharged from said at least one first or second liquid piston to the first separator (2).

9. The device according to any of the preceding claims, where each of the first and second chambers (31, 32) is fluidly connected to a fluid / fluid exchanger (71, 72) which makes it possible to maintain said at least first and second liquid pistons (41, 42), respectively, at ambient temperature, preferably with a tolerated temperature variation of plus or minus 10°C, said fluid / fluid exchanger (71, 72) preferably comprising a pump (83), a fluid / air exchanger (84) or a fluid / fluid exchanger, optionally a motorized fan (85) if said exchanger is a fluid / air exchanger (84) and optionally at least one control valve (86).

10. The device according to any of the preceding claims, where the insert (51, 52) comprises a core of structural material comprising an expanded honeycomb structure.

11. The device according to any of the preceding claims, where said mechanical actuator (1) comprises a magnetically actuated linear motor (23).

12. The device according to any of the preceding claims, where said mechanical actuator (1) comprises a motor associated with a crankshaft.

13. The device according to any of the preceding claims, where said mechanical actuator comprises a motor associated with a worm screw.

14. An installation comprising at least two devices according to any of the preceding claims, where said mechanical actuators (1) of said at least two devices are mechanically linked to operate together, and comprising a first phase separator (2) common to said at least two devices, said common first phase separator being connected to a first outlet (37) of the first chambers (31) of the devices and to a second outlet (38) of the second chambers (32) of said devices, said first phase separator (2) being connected to a common pressurized gas storage tank (5).

15. The installation according to claim 14, comprising at least two devices according to claim 3, comprising a second separator (6) common to said at least two devices, said common second separator (6) being connected to said first and second outlets (37, 38) of said first and second chambers (31, 32) of each of said at least two devices, where said first common separator (2) comprises a first internal pressure which corresponds to the internal pressure of the gas comprised in said common pressurized gas tank (5) and where said second separator (6) comprises a second internal pressure which corresponds to atmospheric pressure.

16. A method for implementing a device according to any one of claims 1 to 13, comprising the following steps: - actuating the mechanical actuator (1), - moving said at least one solid piston (21, 22, 23) causing the movement of said first liquid piston (41) in said first chamber (31) and said second liquid piston (42) in said second chamber (32), said first and second liquid pistons (41, 42) being moved in opposite directions, the first liquid piston (41) compressing said gas (3) in the insert (51) of said first chamber (31) to a first predetermined pressure, the second liquid piston (42) creating a low pressure in said insert (52) of said second chamber (32) to a second pressure, - when said first pressure is reached, opening an air intake device (13) between said first chamber (31) and said first phase separator (2) to discharge pressurized gas (3) from the first chamber (31) to said first separator (2) until said liquid piston (41) passes entirely through said insert (51) and reaches the first outlet (37) of the first chamber (31), and simultaneously the intake of air (14) into said second chamber (32).

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